Trunk circuit



TRUNK CIRCUIT Filec i Nov. 17; 1954 V 3 Sheets-Sheet 1 ALARM CIRCUIT lNl/EN TOR By A. C. POWELL A TTORNEV Jan. 7, 1936. A, P WE L 2,027,197

TRUNK IRcUIT Filed Nov. 17, 1934 3 Sheets-$heet 3 T0 SPL/TTING C/RCUITi;

VINVENTORV c. POWELL A T TORNEV Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE TRUNK CIRCUIT Albert .C. Powell, New

York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a. corporation of llew York Application November 17, 1934, Serial No. 753,460

7 6 Claims.

number from the originating oifice either orally,

or visually as in the case where display call indicator equipment is provided. I In such systems the calling trunks are connected in a predetermined sequence, either to the operators telephone set, in case the called number is to be passed orally, or to the call indicator equipment, when the call is to be displayed visually. In both instances a signal lamp is steadily lighted before the operator for each calling trunk and as soon as a trunk is connected to the operators set, or indicator, the lamp of that trunk is caused to flash and certaincurrent impulses are transmitted back over the trunk to inform the originating operator, or dial equipment, to transmit the wanted subscribers number. The performanceof the foregoing functions in the proper sequence requires an arrangement of sequence relays common to the B operators position. Once the position circuit has started to work on a calling trunk, all other calling trunks are locked out and held in abeyance until the sequence relays have gone through their cycle of operation and the operator has releasedher telephone set, or the indicator, from'the trunk. It may happen that trouble develops in the automatic sequence relays of the position during the handling of a call and the normal cycle of operations is arrested. Under this condition the operator will not receive any calls, although a number of lamps are steadily lighted at her position indicating trunks on which calls are waiting.

In connection with such systems therefore it is desirable to provide some auxiliary means, under control of the operator, whereby in cases of emergency she may manually by-pass the automatic sequence equipment and connect the calling trunks, one by one, to her telephone set or display indicator.

An object of the invention is to provide such emergency answering facilities in systems of the before described character.

A feature of the invention, whereby the foregoing object is attained, resides in the provision of an emergency jack arrangement with which a.

calling trunk plug may be connected, which functions to by-pass the sequence relays of the position and cause t e trunk cond c or o be 1 immediately connected to the operator's telephone or display indicator. 7

The invention will be more clearly understood from the following description when read in connection with the accompanying drawings, in which Fig. 1 shows one of the trunk circuits appearing at an operators position, together with the sequence relays of three trunks, and

Figs. 2 and 3 show the operators position equipment and the emergency jack above-mentioned.

A recorder circuit suitable for use with this position equipment is shown in U. S. Patent 1,968,420, granted to the present inventor on July 31, 1934.

When the operator occupies her position, she inserts her head-set plug 300 in the position jack 31H, thereby completing a circuit from ground through the right winding of repeating coil 302, contacts of jack 3M and plug 300, through the head-set transmitter and back way of con tacts of plug 300 and jack 3!)! to the winding of relay 3G3 and battery. Relay 393 connects direct ground to conductor 384 to prepare the emergency key 386 and to conductor 305 leading to the idle position indicator. It also connects ground from the position splitting and grouping circuit, indicated by the space between the two vertical broken lines at the left of Figs. 2 and 3, to conductor 30'! and the winding of relay 200.

Relay 200 operates and at its inner upper contact connects ground to the windings of relays and 202 to connect the position equipment with the splitting circuit where connections extend in multiple toward all the trunks included in the operators division. Over its second lower contact relay 200 causes the operation of relays 308 and 309, which complete other connections between the control circuit and the splitting circuit.

When, now, an incoming call is directed to the trunk of Fig. 1, a circuit is closed from battery through the upper winding of relay I00, upper left winding of repeating coil IUI, upper back contacts of relays I02 and I03, tip contact of test jack I04, over the tip conductor of the incoming trunk, through the winding of a relay at the distant oflice, back over the ring conductor of the trunk, ring contact of jack I04, lowor back contacts of relays I03 and I02, lower left winding of repeating coil IUI, lower winding of relay I00 to ground. Relay I00 operates, in turn operating relay I05.

' The operation of relay I05 closes a circuit from battery through the winding of relay H3, outer right contact of relay 505, outer right back contact of relay I06, lower back contact and lower winding of relay M4 to ground. Relay H4 is not operated in this circuit but relay II3 does operate, closing a circuit from ground over its right contact through resistance I 40 and lamp I I5 to battery, indicating to the operator that a call is waiting on the associated trunk.

Relay I05 also connects ground over its inner right contact, inner right back contact of relay I06 to the winding of relay I0'I of the sequence relays.' If no trunk lower than this in the chain is connected with the operators position, the circuit of relay I01 extends over the normal contacts of the sequence relays corresponding to relay I08 of all such trunks to battery. Relay I01 operates as soon as this circuit is completed and, if no call is waiting on a trunk higher than this one in the chain, closes a circuit from battery through the winding of relay I08, lower front contact of relay E01, lower normal contacts of the corresponding sequence relays of the earlier trunks, conductor I09, winding of relay 203, back contact of relay 204, to ground. Relay 203 locks to ground at its outer lower front contact and extends its locking ground to the winding of relay 204 which operates, holding open the ground normally supplied to conductor I00.

When relay I 08 operates, it closes a circuit from ground through resistance I40, right contact of relay I I3, outer upper contact of relay 508, Winding of relay MI, conductor I42, inner upper contact of relay 202, upper back contact of relay 230, inner upper back contact of relay 208, winding of relay 233 to battery. Relay 233 operates, in turn operating relays 235 and 236 which areslow to operate. Relay 230, after an interval measured by this slow to operate characteristic, connects direct battery in shunt of the winding of relay 233 and relay 233 releases, in turn releasing relays 235 and 236. With relay 236 released the shunt is removed from relay 233 and the cycle repeats as long as the circuit is maintained. The direct battery furnished by relay 236 also shunts lamp H5 causing it to flash. Relay I H also operates and releases in this flashing circuit, causing the pilot lamp I03 to flash likewise.

When both relays I01 and I08 have operated, a circuit is closed from ground over the upper contact of relay 50?, inner upper contact of relay I08, right winding of relay IIO, conductor III, middle lower contact of relay 20I, back contacts of relays 205 and 206, lower back contact of relay 208 to battery. Relay IIO operates, locking from the same ground through its left winding and first left contact, conductor I I 2, inner lower front contact of relay 208, winding of relay 209, lower back contact of relay 2I0, to battery. Relay IIO connects the multiple contacts leading from the position circuit, individually to this trunk.

Since the circuit of relay H3 as above traced includes the back contact of relay H4, which is opened as long as the plug IE6 is in a multiple jack, the operation of relay I I3 indicates that the plug has been removed from the multiple and the call may progress normally. Relay I 53 transmits this. information to the control circuit by connecting ground to conductor I I? over the sec-- ond left contact of relay H0, conductor III extending over the inner lower front contact of relay 200 to the lower winding of relay 2II and battery. I I

Relay 209 operates in the locking circuit of relay '0 above traced, in turn operating relay 2I2.

At its middle upper contact relay 2I2 completes the circuit of relay 2I6 and at its inner upper contact prepares locking circuits for relays 2i? and 2I8. At its inner lower contact relay 2I2 operates relay 206 and at its lowermost contact 5 prepares a circuit for the emergency operation of the control circuit. Relay 2I6 operates relay 2I0.

Relay 206 looks over its inner upper front contact, upper back contact of relay 208 to ground 10 over the outer upper front contact of relay 200.

It also closes a locking circuit for relay 2 I I which extends from battery, through the upper winding and inner upper front contact of relay 2I I to ground at the outer upper front contact of 15 relay 206. In addition, it closes a circuit from ground at its outer lower contact through the winding of relay 3I6 to battery. Relay 3I6 disconnects the talking conductors leading toward the operators repeating coils from one connection :0 through the grouping circuit and extends them toward the connection leading toward the trunk being served.

The fact that the trunk is one incoming from a panel type oflice is indicated to the control cirg5 cuit when relay I I0 operates by the completion of a circuit from battery through the winding of relay I03, fifth left contact of relay II 0, conductor I I8, outer upper front contact of relay 202, normal contacts of relay 2I0 over conductor 220 30 through the recorder circuit and back over conductor 22 I to the winding of relay 2 I3 and ground. Relay 2 I3 operates but relay I 03, being marginal, cannot operate in series with relay 2I3. Relay 2I3 closes a circuit from ground at the outer 36 upper contact of relay 2 I2, front contact of relay 2I3, outer upper contact of relay 2! I, Winding of relay 222 and battery. Relay 222 at its upper front contact, locks directly to the contact of relay 2I2 and at its inner lower contact closes 40 an obvious circuit for relay 223. At its outer lower contact, relay 222 closes a circuit from ground over this contact, lower back contact of relay 224, winding of relay 225 and battery. Relay 225 disconnects conductors H9 and I20, which have 5 been extended by the operation of relay 20I to the upper armatures of relay 225, from the op erators telephone circuit and extends them over the front contacts of these armatures to con ductors 226 and 221, leading to the recorder cir- 50 cuit in preparation for receiving the wanted number from the panel sender. Relay 225 also closes a circuit from ground over its lower contact to the winding of relay 3 I1 and battery. Relay 3I'I further disconnects the operators tele- 55 phone from the talking conductors in the con trol circuit and connects high resistance 3I8 across these conductors to stabilize condenser 246 and prevent a click in the operators receiver.

Relay 223 connects ground over its inner upper 00 contact to conductor 228 to operate a relay in the recorder circuit which in turn connects direct ground to conductor 22.0 in shunt of the winding of relay 2I3, releasing relay M3 and operating relay I03. Relay 223 also prepares the peg count circuit for this type of trunk. The operation of relay I03 disconnects the incoming trunk conductors from battery and ground through the windings of relay I00 and connects them over conductors H0 and I20 to the receiving relays of the recorder circuit, thereby signaling the distant sender that the designation may be sent out. The disconnection of the trunk conductors from relay I00 permits that relay to release, but relay I05 is maintained operated in a circuit exrelay I05 and battery; Relay 230 operates in this circuit, looking to ground at its upper front contact.

7 When relay 2 I 3 releases, a circuit is closed from ground at theouter upper front contact of relay 2I2, back contact of relay 2I3, back contact of relay 2, winding of relay2I5 and battery. Relay 2I5 connects battery over its front contact to the winding of relay 3 and ground. Relay 3 connects ground to conductor 3I2 leading to the position indicator circuit and also closes a circuit from battery through the winding of relay 3I3, normal contacts of relay 3I4, lower contact of relay 3! I, to ground at the normal contacts of relay 3I5.

Relay 3I3 locks to ground at its upper front contact, over the contacts of relays 3I4 and 3 but independent of re ay 3I5. It also closes a circuit from the tone source indicated by high speed interrupter 3I9, primary winding of tone coil 320, first lower contact of relay 3I3, normal contacts of relays 32! and 323 to ground through resistance 320. Relay 3I3 also closes a circuit from ground through the lower left winding of repeating coil 326, network 327, condenser 325, secondary winding of tone coil 320, second lower contact of relay 3I3, inner upperback contact of relay 328, inner'lower front contact of relay 3I8, left front contact of relay 3I'I to ground. The tone. induced in the secondary winding of coil 325 is transmitted to the, operators telephone through coil 328 to warn her that the wanted number isabout to be displayed.

Relay 3I3 also closes a circuit from ground at the lower back contact of relay 3I0, fourth lower contact of relay 3I3, outer back contact of relay 328, winding of relay 32I andbattery. Relay 32! opens the primary tone circuit and extends its operating ground to the winding of relay 322. Relay 322 recloses the tone circuit and operates relay 323. Relay 323 again opens the tone circuit and operates relay 328. Relays 32I, 322 and 323 are slow to operate, thereby'providing for two measured impulses of tone. Relay 328 disconnects the secondary of the tone coil from the talking conductors and connects the operators head-set thereto, but this action is ineffective since the talking conductors are opened at the contacts of relays 3I'I and 225.

Relay 328 at its uppermost armature opens the circuits of relays 32I and 322 and closes a circuit from battery through the winding of relay 323, outer upper front contacts of relay 328, fourth lower contact of relay 3I3 to ground at the back contact of relay 3I0, thereby holding relay 323 operated which in turn holds relay 328 operated. At its third upper front contact, relay 328 connects battery to the winding of relay 3, completing a circuit which extendsover the inner upper back contact of relay 3I4, back contact of relay 330 to ground at the middle lower contact of relay 2I6. Relay 3M operates, looking to ground over its middle front contact. It also connects ground to the winding of relay 3I5, and over the normal contacts of relay 3I5 and the lower front contact of relay 223 to conductor 23I leading to the call indicator peg count meter.

thus insuring that the meter is operated only once. Relay 3I5 also closes a circuit over its lower front contact through the winding of relay 205 and battery, Relay 205 looks to ground at the middle upper front contact of relay 206. 5

Relay 3M opens the circuit of relay 3I3 previously traced, but by means of its make before break contacts extends the circuit over its outer upper front contact, back contact of relay 330 to ground at the middle lower contact of relay l0 2 I8 before the first circuit is broken, holding relay 3I3 operated.

When the complete designation has been received, the circuit of relay I03 is opened in the recorder circuit and that relay releases, restoring 15 the connection of thetrunk conductors to relay I00. Relay I00 reoperates', connecting ground to the winding of relay I05, holding that relay operated and shunting the winding of relay 230 which releases. 20

The operator, having seenthe wanted number displayed by the recorder, prepares for signaling the subscriber by operating the proper ringing key, for example key I23. She then operates the position release key 33I, closing a circuit from 25 ground over the key contact, through the split-: ting circuit, outer upper contact of relay 308, upper back contact of relay 332, upper winding of relay 333 to battery. Relay 333 closes a circuit from battery, through the upper winding of reso lay 330, lower back contactof relay 332, lower winding and contact of relay 333, outer lower front contact of relay 205, outer lower contact of relay 2 back contact of relay 232 to ground at the back contact of relay 230. Relay 330 looks in a 35 circuit from battery through its lower winding and contact, to ground at the middle lower contact of relay 205. Relay 330 opens the circuit of relay 3I3 causing that relay to release, in turn releasing relays 323 and 328. Relay 328 in turn 0 releases relays 3I4 and 3I5. 7

Relay 330 extends its locking ground over the outer lower contact of relay 20I to the winding of relay 232 and battery. With relay 230 released, relay 232 closes a circuit from ground at- 45 the upper back contact of relay 230, inner lower front contact of relay 232 through the winding of relay 208 to battery. It also extends this same ground over its outer lower front contact to the lower winding of relay 332 and battery. 5( Relay 332 looks in a circuit from battery through its upper winding and upper front contact, outer upper contact of relay 308 to ground on the release key 33! therefore remaining operated as long as the key remains depressed. Relay 332 55 opens the operating circuits of relays 333 and 330 and the locking circuit of relay 333 releasing relay 333: Relay 232 also provides an additional holding circuit for relay 3 I1.

Relay 208 in operating opens the locking cir- 0 cuit of relay.206 but relay 206 remains operated under the control of relay 2I2. Relay 208 also disconnects battery from the operating circuit of relay IIO, and opens the circuit of relay 233, thereby stopping the flashing of lamps H5 and 05 I 43 and releasing relay I4I. It also connects ground from the outer upper contact of rely 200, upper front contact of relay 208, lower back contact of relay 230, outer lower contact of relay 202, conductor I24, third contact of relay H0, winding of relay I06 and battery. Relay I03 looks over its left front contact to ground at the left front contact of relay I85, and opens the circuit of relay I01 which releases, in turn releasing relay I08 and relay IIO, completing the dis- :5

connection of the trunk from the position circuit. Relay I06 also'opens the circuit of relay H3 which releases. In addition it closes a substitute circuit for lamp II5 extending from ground through the lower winding of relay II4, back contact of relay II4, outer right front contact of relay I06 to lamp I I5 and battery. The release of relay I01 opens the circuit of relay 203 which releases, in turn releasing relay 204. Relay 204, being slow in releasing holds ground disconnectedfrom conductor I09 momentarily to insure the operation of the sequence relay corresponding to relay I08 associated with the lowest numbered trunk awaiting connection tothe control circuit.

'The release of relay IIO opens the operating path for relay I06 and also releases relay 209. Relay 209, releases relay 2I2 and that relay in turn releases relays 222, 2I6, 2I5 and 206. Re-

.lay 206 in releasing releases relays 2H and 3I6 and opens the holding circuit of relay 205 which in turn releases relays 330, 232 and 208. Relay 2I6 opens the circuit of relay 2 I9 while relay 2I5 releases relay 3| I. Relay 222 releases relays 223 and 225, relay 225 in turn releasing relay 3I1 and opening'the tip and ring conductors leading to the recorder circuit. Relay 223 also releases the relays of the recorder circuit.

The operator next tests the wanted line by touching the tip of plug II6 to the sleeve of the multiple jack. If the line is busy, battery on the sleeve of the jack will complete a circuit over the tip of plug I I6, upper normal contact of relay I I4, conductor I22, inner lower contact of relay 308, network 334,- upper left winding of repeating coil 326 to ground, producing a click in the operators receiver.

If the line is idle, no such click is heard and the operator inserts the plug H6 in the jack of the wanted line. The grounded jack sleeve characteristic of the idle line completes a circuit over the sleeve of plug II 6, upper Winding of relay II4, lamp II5 and battery. Relay II4 operates, opening the circuit previously traced for lamp II 5 and closing a circuit from ground on the sleeve of the multiple jack, sleeve of plug II6, upper winding of relay I I4, outer right front contact of relay I05, lower front contact of relay II 4, back contacts of relays I25 and I26, in parallel with the winding of relay I26, winding of relay I21 to battery. The closure of this circuit for relay I21 shunts lamp II5, darkening it, but

relay I21 operates, closing a circuit from ground over the right contact of key I23, winding of Y relay I28, inner lower front contact of relay I21,

normal contact of relay I29, to pick-up conductor I30, to which battery is connected by the ringing circuit previous to the start of the ringing period. A parallel circuit is closed from ground through the Winding of relay I29. When the pull-up battery is connected to conductor I30, relays I28 and I29 operate and relay I29 closes a locking circuit for both relays to battery over its outer lower front contact. With relays I21, I28 and I29 operated, the ringing circuit is closed from ground over conductor I32, left normal contacts of keys I34 and I35, right normal contacts of key I36, outer lower front contact of relay I21, ring of plug II6, through the ringer at the called substation, tip of plug I I6, upper front contacts of relays I I4 and I21, right normal contact of key I34, left operated contact of key I23, inner front contact of relay I29, winding of relay I25, front contact of relay I26. to conductor I 3| which leads to the two-ring commutator of the ringing machine.

The wanted subscriber is signalled over this circuit, ringing tone being transmitted back toward the calling subscriber through condensers I31 and I38, and, when he removes his receiver, the resistance of the circuit is decreased to permit relay I25 to operate. Relay I25 opens the shunt around the winding of relay I26 and that relay operates, looking to battery at its front contact. This battery shunts the winding of relay I21 which releases, disconnecting the called line from the ringing circuit, releasing relay I25, and reclosing the shunts around condensers I31 and I38. Relay I21 in releasing also opens the circuits of relays I28 and I29.

With relay I21 released, relay I39 operates in series with the called substation and closes a circuit from ground at its contact, left back contact of relay II3, inner right front contact of relay I06, winding of relay I02 and battery. Relay I02 reverses the connection of battery and ground through the windings of relay I to the incoming trunk as a signal to the district selector that the called subscriber has answered. Relays I02, I96, I05, I06, I39, I26 and H4 of the trunk circuit remain operated throughout the call.

When the called subscriber restores his receiver at the termination of the conversation, relay I39 releases, in turn releasing relay I02 to signal the district selector. When the selector releases, opening of the circuit of relay I 00, that relay releases, in turn releasing relays I and I06. With relay I06 released, relay I26 also releases and the shunt is removed from lamp I I5 which now lights as a disconnect signal to the operator. When the operator removes the plug from the jack, relay I I4 also releases and lamp II5 is extinguished, restoring the trunk completely to normal.

If the trunk of Fig. 1 is reselected while plug I I6 is still in the jack of the wanted line or a busy back jack, relay II4 will be held operated from the sleeve of the jack. Relays I00, I05, I01, I08, I I0, 203, 204 and 209 operate as above, and lamps II5 and I43 flash to indicate the incoming call. Relay I I3 cannot operate with relay I I4 operated and therefore relay 2 cannot operate. When relay IIO operates, relay 2I3 is operated in series with relay I03. Since relay 2 is not operated, relay 222 cannot operate and no signal can be transmitted to the sender. Likewise, no tone can be given to the operator .and release key 33I is inelfective. The operator, observing the flashing lamp, will withdraw the plug of the trunk cord from the multiple jack permitting relay II3 to operate and the remaining operations to take place as previously described.

If, for any reason, the district selector does not make trunk closure following the transmission of the wanted number for example, because the call has been abondoned, relay I00 cannot reoperate to shunt relay 230, and the release key 33I is ineffective. Similarly, if the recorder is not satisfied, it does not open the circuit of relay I03, relay I00 cannot reoperate and the call cannot be completed.

In this case, the operator may close key 238, completing a circuit from ground over key 238, outer upper contact of relay 223, winding of relay 224 and battery. It may be noted that, since relay 223 is operated only when the control circuit is used with call indicator trunks, key 231 is effective only in connection with call indicator calls. Relay 224 looks over itsinner lower contact to the outer upper front contact of relay 206 and releases relay225, disconnecting the trunk from the recorder. With relay 224 operated, battery and ground through coil 23'! are connected to the trunk conductors. The release of relay 225, in turn releases relay 3II which extends the trunk conductors to the operators telephone. If the subscriber is still connected with the trunk the operator may obtain the number of the line,

wanted. Having done so, she operates key 239 closing an obvious circuit for relay. 240 which locks under the control of relay 206. Relay 240 prepares a circuit for relay I06and closes battery to the windings of relays 209 and I I0 to hold those relays operated until after relay I06 has been operated. With relay 224 operated, the release key 33I is made effective and, when relay 232 operates, a circuit is closed from battery through the winding of relay 2I0, inner upper front contact of relay 224, to ground at the upper front contact of relay 232. Relay 2I0 opens one connection of battery to relay IIO, opens the circuit of relay I03 permitting that relay to release and restore the talking connection to the trunk,

and connects resistance 242 and condenser 24I around coil 23! to protect the contacts of relay In order to take care of calls which may reach the trunk of Fig. 1 when no operator is located at the position, the withdrawal of the telephone plug from the position jack releases relay 303 in turn releasing relaps 200, 20I, 202, 308 and309. Relay 309 at its lower back contact extends ground through the splitting circuit to the winding of relay 3I0 and battery. Relay 3I0 closes a circuit for reoperatingrelays 20I and 202, and relay 202 closes the previously traced flashing circuit for lamps I I5 and I43. Relay 3I0 also extends the night alarm conductor 335 to a contact of relay 2I6 so that, if a call is directed to this position the night alarm will sound and the trunk lamp flash. Relays 209, 2I2,',2I6 and 206 operate as previously described. Since relay.200 is not operated, relay .2 cannot operate and the call awaits the attention of the operator.

If the automatic listening equipment in the position fails, the operator operates the splitting basis. When a trunk is seized, relays I00, I05 and H3 operate as before and lamp II5 islighted steadily to ground over the right front contact of relay H3 and resistance I40. Since the sequence relays are assumed to be at fault, the lamp II5 will not flash and relay IIO will not operate. Key 306 is then operated, in turn operating relay 330, opening the sequence chain. The operator then inserts plug I I6 in emergency jack 243. Since the sleeve of this jack is not grounded, relay II4 does not operate. A circuit is closed, however, from battery through the lower right winding of repeating coil IOI, winding of relay I39, lower back contact of relay I21, ring of plug H6 and jack 243, lower winding of.relay 244, normal contactsof relay 2I9, to ground at the lowermost contact of relay200. Relays I39 and 244 operate in this circuit. Relay I39 closes a circuit from ground at its front contact, outer left front contact of relay H3, right winding of relay. IIO, conductor III and thence to battery aspreviously traced. The circuit then functions. as previously described. When relay 2I6 operates, it closes a circuit for relay 2I9 whichlocks overits lower front contact and the contact of relay 244 to ground. Relay 2I9 also closes a substitute circuit from ground at the lowermost contact of relay 200, outer lower contact of relay 2I2 and the front contact of relay 2| 9 to the lower winding of relay 244, in 5 place of the circuit above traced over the normal contact of relay 2I9, thus placing the holding of relays 244 and I39 under the control of relay H2. The operation of the release key causes the operation of relay I 06 and the release of m relay II3 as previously described, relay H3 opening the circuit of relays H0 and 209. Relay 209 in turn releases relay 2I2. When relay 2I2 releases the shunt around the upper winding of relay 244 is removed. Relay 244 remains operated through its two windings, but, due to the high resistance of the upper winding, relay I39 is released. Although the circuit of relay I02 may be closed momentarily, following the closure of the back contact of relay II3, the release 20 of relay I39 follows 50 closelythat it does not remain operated for a suflicient length of time. to cause the call charging apparatus at the originating ofiice to function. When plug H6 is removed from jack 243 for insertion in the jack 25 of the wanted. line, relays 244 and 2I9 release and the call is completed in the usual manner. The control circuit of Figs. 2 and 3 will serve four types of trunks, namely, trunks of the type shown for completing calls from panel ofiices 30 equipped with call indicator impulsers, similar trunks incoming from tandem oifices equipped with call announcer machines, similar trunks incoming from manual omces and trunks of a different type also incoming from manual ofiices. 35

The operation of the control circuit in connection with the trunk types not shown is very similar to the operation described above. In the case of trunks incoming from tandem ofiices, conductor I I8 is grounded directly, the back contacts 0 of relay I03 are permanently bridged and the winding of relay I02 is connected over the outermost contact of relay IIO to conductor I44. Therefore, as soon as relay IIO operates, relay I03 is operated to connect the trunk conductors 5 with the control circuit and relay 2l4 operates in a circuit from battery through the winding of relay I02 connected to conductor I44, middle upper contact of relay 202, winding of relay 2I4, upper normal contacts of relay 2I8 to ground. Relay 2'I4 in turn operates relay. 3Il1and relay 2I'I, which locks under the control of relays 2I8 and 2I2 and provides a supplementary holding ground for relay 2I4. Relay 3|! performs the functions previously described. Relay 209 op- 55 crates in the locking circuit of relay IIO in turn operatingrelays 2I2, 2I6, 206;and 2I9. Relay 2H operates relay 245 which closes a second holding circuit for relay 3|? and prepares the peg count circuit. If relay 2 is operated to indicate that the trunk plug isnot in a multiple jack, relay 245 extends its operating ground over the inner lower contact of relay 2 in shunt, o1 relay2l4 which releases, to operate relay 2l5 and initiate the generation of the order tones. Relay I02 is operated, reversing the battery and ground connection to the tandem ofiice. When the order tones have beengeneratedrelay 205 operates as previously described, operating relay 2l8 which looks to the inner upper contactof relay 2I2, and releasesrelays 2I'I, 245 and I02 to terminate the signal to the tandem ofiice which nowtransmits the wanted number by call announcer. The remaining-operations are, substantiiallv h amea i he sell ndies??? im i- 5- For astraightforward trunk, incoming from a manual ofiice, conductor H8 is grounded and the back contacts of relay I03 bridged as for the call announcer trunk. Neither relay 13 nor relay 192 is connected through to the position control circuit and therefore neither relay 2l3 nor relay 2b?- is operated. Therefore relay 255 operates directly after relay 2l2 operates and starts the tone relays. Relay 3 I! is not operated and therefore the order tones are transmitted over the front contacts of relay 3 l6, back contacts of relay 3H, back contacts of relay 225, front contacts of relays 2M and H13 to the incoming trunk and the operator at the manual oflice. It is apparent therefore that with manual operation, the transmittal of the order tones and wanted number is not delayed by the presence of the trunk plug in a multiple jack. However, until relay 2!! is operated, the operation of key 33! is inefiective to operate relay 330 and relay I06 cannot be operated to permit the ringing relays to operate.

In handling calls on the other type of trunk incoming from'manual ofiices, relays 203 and 204 are operated from the sequence relays. Battery connected to conductor 33'! closes a circuit over the inner upper front contact of relay 309, inner upper back contact of relay SIB to the winding of relay 3 and ground. Relay 3| l initiates the operation of the tone relays. When the trunk is connected through to the position control circuit, battery connected to conductor 338 completes a circuit over the third lower contact of relay 200, lower back contact of relay 234, upper back contact of relay 332, winding of relay 339, outer upper back contact of relay 3M and ground. Relay 339 looks to ground at its outer contact. Since relay 3I6 is normal, the tones are transmitted over the normal contacts of relays 328 and 3I6 and the front contacts of relay 309 to the splitting circuit and thence to the trunks of the type not shown. When relay 328 operates, after theorder tones have been sent out, it connects the trunk to the operators telephone and operates relay 3 I4. With relay 3| 4 operated the'holding circuit for relay 3l3 is extended to ground at the inner contact of relay 339. Relays 3E5 and 205 are operated as before. With this type of trunk the insertion of the trunk plug in the jack of the wanted line releases relay 339 restoring the control circuit to normal.

What is claimed is:

1. In a telephone trunking system, an operators position, a plurality of calling lines incoming thereto and terminating in connecting plugs thereat, call receiving equipment thereat, control means common to said position for extending said calling lines to said receiving equipment, relay means associated with said lines and automatically responsive to calls thereon to connect said calling lines to said control means one at a time in a predetermined sequence and to cause said control means to extend such lines to the receiving equipment, an emergency jack arrangement, and circuit means associated with each calling line and responsive to connection of its associated plug with said emergency jack to connect such line to the control means and to cause the control means to extend the line to the receiving equipment independent of the sequence relay means.

2. In a telephonetrunking system, an operators position, a plurality of calling lines incomingthereto and terminating in connecting plugs thereat,'a supervisory relay for each calling line, call receiving equipment thereat; controlmeans common to said position for extending said call ing lines to said receiving equipment, relay means associated with said lines and automatically responsive to calls thereon to connect said calling lines to said control means one at a time in a predetermined sequence and to cause said control means to extend such lines to the receiving equipment, an emergency jack, means responsive to the connection of the plug of the calling line with said emergency jack to operate said supervisory relay, and means under the control of said supervisory relay to connect such line to the control means and to cause the control means to extend the line to the receiving equipment independent of the sequence relay means.

3. In a telephone trunking system, an operators position, a plurality of calling lines incoming thereto and terminating in connecting plugs thereat, a supervisory relay for each calling line, call receiving equipment thereat, control means common to said position for extending said calling lines to said receiving equipment, relay means associated with said lines and automatically responsive to calls thereon to connect said calling lines to said control means one at a time in a predetermined sequence and to cause said control means to extend such lines to the receiving equipment, an emergency jack, means responsive to the connection of the plug of the calling line with said emergency jack to operate said supervisory relay, means under the control of said supervisory relay to connect such line to the control means and to cause the control means to extend the line to the receiving equipment independent of the sequence relay means and means to release said supervisory relay prior to the disconnection of said plug from said emergency jack.

4. In a telephone trunking system, an operators position, a plurality of calling lines incoming thereto, and terminating in connecting plugs thereat, a supervisory relay for each calling line, call receiving equipment thereat, control means common to said position for extending said calling lines to said receiving equipment, relay means associated with said lines and automatically responsive to calls thereon to connect said calling lines to said control means one at a time in a predetermined sequence and to cause said control means to extend such lines to the receiving equipment, an emergency jack, means responsive to the connection of the plug of the calling line with said emergency jack to operate said super visory relay, means under the control of said supervisory relay to connect such line to the control means and to cause the control means to extend the line to the receiving equipment independent of the sequence relay means and means resposive to the disconnection of said line from said control means to release said supervisory relay prior to the disconnection of said plug from said emergency jack.

5. In a telephone trunking system, an operators position, a plurality of calling lines incoming thereto and terminating in connecting plugs thereat, a supervisory relay for each calling line, call receiving equipment thereat, control means common to said position for extending said calling lines to said receiving equipment, relay means associated with said lines and automatically responsive to calls thereon to connect said calling lines to said control means one at'a time in a predeterminedsequence and to cause said control means to: extend such lines to the receiving equipment, an emergency jack, means responsive to relay, means under the control of said supervisory relay to connect such line to the control means and' to cause the control means to extend the line to the receiving equipment independent of the sequence relay means, means to disconnect said line from said control means, charge controlling means under the control of said supervisory relay after said disconnection takes place, and means to prevent the effective premature operation of said charge controlling means.

6. In a telephone trunking system, an operators position, a plurality of calling lines incoming thereto and terminating in connecting plugs thereat, a supervisory relay for each calling line, call receiving equipment thereat, control means common to said position for extending said calling lines to said receiving equipment, relay means associated with said lines and automatically responsive to calls thereon to connect said calling lines to said control means one at a time in a predetermined sequence and to cause said control means to extend such lines to the receiving equipment, an emergency jack, means responsive to the connection of the plug of the calling line 5 with said emergency jack to operate said supervisory relay,'means under the control of said supervisory relay to connect such line to the control means and to cause the control means to extend the line to the receiving equipment inde- 10 pendent of the sequence relay means, means to disconnect said line from said control means, charge controlling means under the control of said supervisory relay after said disconnection takes place, and means responsive to said disl5 connecting means to prevent said supervisory relay from effectively operating said charge controlling means as long as said plug remains in said emergency jack.

ALBERT C. POWELL. 

